This chapter begins with a basic definition of access control. On the surface, the process of establishing the identity of the caller, checking for authorization, and opening or closing the gate is extremely simple. So simple, in fact, that the qualification requirements for a nightclub's doorman tend to be more concerned with physical mass than cranial capacity. We have seen how the three-party model of caller, security guard, and authorizer has been adopted first for dial-up modem authentication, second for LAN access authentication using IEEE 802.1X, and finally for wireless LAN authorization using IEEE 802.11 and IEEE 802.1X.

This chapter also reviewed how the messages between the three controlling parties are carefully defined using the protocols EAP and RADIUS. We observed that wireless LAN places an additional burden on the process because it is so vulnerable to session hijack. In the case of WPA and RSN, it is necessary to establish a set of secret keys between the access point and the mobile device to protect against hijack. It this way, the authorization obtained during the access control procedure becomes like an access pass that can be used over and over with each packet of data sent.

The establishment of the secret session keys and their binding to the access control procedure has been one of the challenges of developing new security protocols (see Chapter 10). In Chapter 9, we look at the upper-level authentication protocols that ensure beyond doubt that the entities that you intend to authorize really are who they say they are.

    Part II: The Design of Wi-Fi Security